Traffic control system



Jan. 2, 1934.

P. THOMAS TRAFFIC CONTROL SYSTEM Filed Feb. 14, 1931 2 Sheets-Sheet l INVENTOR Phil/405 777 00705. 1

'ATTORNEY Z/V/T/VESSES.

TRAFFIC CONTROL SYSTEM Filed Feb. 14, 1-931 2 Sheets-Sheet 2 W/TNESSES.

INVENTOR 2. Q Phi/0,05 Thqmas.

Patented Jan. 2, 1934 [TED sTA'res PAT r C QONTROL SYSTEM Phillips Thomns, Edgewood, Po,

assignor to Westinghouse Electric & Manufacturing Company, a corporation oi llennsylvonia Application February 14, 1931. Serial No. 515,714

1 claim. (CL ill-339) My invention relates to trafiic-control systems and has particular relation to traflic-control systems oi a. type utilized at inejor highway intersections.

6 Under ordinary circumstances, tremc-control systems are provided with a specific design directed to the characteristics of the highway intel-section at which they are intended to be utilmed. The system constructed according to my invention is peniculsrly adapted to be utilized at an intersection where the trafiic along one lane is comparatively heavy and the trafflc along the intersecting lane is comparatively light, at certain periods of the day. At other periods of the day, the treffic along the latter lane is compare.-

-tively heavy and the treflic along the former lane is comparatively light. During the remaining periods, the traffic along both lanes is substen tislly-oi equal density.

It is, accordingly, an object of my invention to provide it ironic-control system particularly adapted to be utilized at a. highway intersection at which the trams along one lane is heavy, as compared with the trams along an ouxilidry lens at certain periods, while the converse is true at certain other periods.

Another object of my invention is to provide a.

theme-control system perticularlyadapted to be utilized at an intersection wherein the ratio of the density of tremc in one direction to the density of trefic in the remaining direction varies from s. comparatively large improper fraction to a comparatively small proper fraction.

A more specific object of my invention is to provide apparatus of a'type responsive to the condition of the traffic along a. plurality of intersecting lanes; said apparatus being adapted to regulate the condition of a homo-signalling device thst normally operates a stop signal for all of the lanes of the intersection.

Another specific object of my invention is to provide vehicle-actuated tramc-control apparatus adapted to be utilized at the intersection of s plurality of lanes; the apparatus being of such structure that a. trsfic-signalling device shall be controlled by a. vehicle moving along one lane, to

indicate 2. go signal for that particular lane and to indicate a "stop signal for the intersecting lanes which signals shall continue to be displayed for a. period of time predetermined by the period required by the vehicle in passing through the intersection.

More concisely stated, it is an object of my invention to provide for an intersection vehicleopereted tramc-control apparatus, of a type having a. plurality of possible conditions of operation; the particular conditions of operation to be utilized at a. given time being dependent on the condition of the treiiic along the lanes forming the intersection at the-particular time.

According to my invention, I provide a tremocontrol system comprising a plurality of street devices, located along the lanes of a. particular intersection and adapted to be controlled by vehicles moving along the lanes. .The street devices ere essocicted with e. syste of relays, with e. program controller and with a signalling device. Under normal circumstances, thesignalling device displays a stop signal for all lanes passing through the intersection. A vehicle moving along one intersection causes actuation of the street device which, in turn, responds by coecting with a. system of relays and causing e g0 signal to be displayed along the purticuler highway along which the vehicle is mov= .system is not immediately changed, but the trsmc-slgnelling device is connected to the pro-' gram controller. At the instant that the connection is made, a caution signal is displayed for a short time, after'which the go signal is displayed for a. predetermined period of time along the lane along which the first vehicle eppeered. At the termination of this period the go signal is transferred to the intersecting lane along which the second vehicle appeared. I accomplish this object by regulating the direction of rotation of the program controller in accordance with the initial condition of the lanes at the intersection.

' To give a. concrete example, I shall assume that the system is disposed at an intersection of two lanes A and B. When there is no traffic along the lanes, 9. stop signal is displayed for both lanes. If a vehicle now appears along the lane A, the system of relays is energized and, in turn, actuates the signalling device to cause a. go signal to be displayed for the lane A and a stop signal to be displayed for the lane B. The signal persists for a. predetermined time of sufllcient length to give the vehicle that actuated the street device suflicient time to pass through theintersecticn. I

' If, during this period of time, a vehicle appears along the lane B, the program-control motor is actuated, and a caution signal is displayed. Moreover, by the initial condition of the lane A, the interconnectionof the starting windings the caution period,

' certain of the four relays trafic signals.

and the main windings of the program-control motor is so adjusted that its direction ofrotation is predetermined in such manner that, after the signals continue to indicate go for the A highway and stop for the B highway for the period-of time necessary for the original vehicle to pass through the intersection.

It will be furthermore noted that the position in which the disk. of the program-control motor stops can only be predetermined within 180. That is to say, the program-control motor stops in a position determined by the last highway along which a vehicle appeared when it was in active condition. I have, consequently, incorporated a reversing relay in the system that is so interconnected with the relays determining the direction of rotation of the motor in accordance with the initial condition of the highways as to cause the motor to rotate in the proper direction to actuate the signals in their proper succession.

The specific embodiment of my invention described herein incorporates a plurality oi pairs of control devices, (in this case, of the photosensitive type), each pair being associated with a particular lane and being adapted to actuate a relay. Each relay in turn, adapted to excite the coil of a time-delay relay which is energized instantly but reverts to its deenergized condition after a predetermined time.

. When only one time-delay relay is energized, it causes its corresponding relays in two pairs of interlocked relays to be energized. One pair of interlocked relays are associated with four relays that independently regulate the condition of the signalsat the intersection, each relay of the interlocked pair being adapted to regulate the activity of two relays associated with the signals of a particular lane.

. The interlocked relays of the remaining pair are adapted to regulate the direction of rotation of a program-control motor, through the contactors of a reversing relay. The state of excitation of the relay is predetermined by the orientation of the program-control disk in its latest resting position. a

When both time-delay relays are energized, the coil of a third time-delay relay becomes excited and, in turn, causes a plurality of latch relays to be energized. a

One of the latch relays opens the normal circuits through the coils of the four relays associated with the signals certain of which were energized by one pair 0 interlocked relays, and closes the circuit throug the windings of the program controller. The remaining latch relay completes circuits through the contacting segment of the program-control disc and through the coils of associated with the When the program-control motor is again deenergized, the tripping devices of the lock relays are released by the closing of a circuit through contactors of the four relays associated with the trafilc signals.

The novel features that I consider characte istic of my invention are set forth with particularity in the appended claim. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof will best be understood from the following description of a specific embodiment, when read in connection with the accompanying drawings, in which Figure 1 is a schematic view showing a vertical 8 section of a lane that traverses a highway intersection at whichan embodiment of my invention is disposed, and

Figs. 2 and 3, jointly constitute a diagrammatic view showing the principal elements of a control 9 system constructed according to my invention.

The apparatus shown in the drawings comprises a signalling device 1, including a plurality of signals 3, 5, 7, 9, and 11 adapted to be displayed at the intersection 12 of the highways 13 5 and 15, containers 1'3, 19, 2?. and 23 having disposed; therein photo-wrisitive devices 25, 23, 29 and 31 and containers 33, 35, 3'? and 39 having sources of light all, 43, 45 and 4'? disposed therein that are adapted to excite the photo-sensitive 109 devices 25, 27, 29 and 31. When the light beam between one source, such as ll, and one associated photo-sensitive device 25 is interrupted by a vehicle 4.9, as shown in the drawings, the system of signals 1 is actuated to produce the necessary signal displays for the particular highway 13 with which the tube 25 and the source i1 are associated.

In Figs. 2 and 3, the intersection 12 isshown in detail. The signalling device the center of the intersection and, for purposes of clarity. has been shown in detail.

Under normal circumstances, the photo-sensitive devices 25, 2'7, 29 and 81 disposed along the lanes 13 and 15 are in an excited state, and, in consequence thereofl'the exciting coils 51 and 53 of a plurality of relays 55 and 57 associated with the devices are in an energized condition.

As is shown in the drawings, a single relay coil 51 or 53 is connected in series with the photosensitive devices 25 and 31, or 2'? and 29 disposed along a, single highway 13 or 15 on both sides of the intersection 12. The relay coil 51 or 53, connected in series with the tubes 25 and 31, or 27 and 29, is, therefore, deenergized by the interruption of the light passing through a single tube.

It is well to point out that it is necessary that the system be actuated by a vehicle appearing along either section of a lane 13.0r 15. Advantage is therefore taken of the fact that the interruption of'the light passing through one photo-tube of a group connected in series relationship is sufiicient to open the series circuit. It is to be noted, however, that this particular feature through the coils 51 and 53 of the mechanical relays 55 and 5'7. Under ordinary circumstances, these devices are adapted to actuate an electrical relay, (that is to say, a grid-controlled electricdischarge tube, for example) and the current from the tube is adapted to energize a mechan- 50 1 is illustrated at 110 I neaaaee ical relay. The specific form of the mechanical relays that is shown is, therefore, only to be regarded as symbolical, and it is to be borne in mind that relays that are ordinarily used in the present connection are 0! the electronic type.

As shown in Figs. 2 and 3, the system is in its normal condition, that is, the stop signals 3 and Tare indicated for both of the highways 13 and 15. g

The stop signal 7 along one highway 15 is energized from the following circuit: from one bus 59 of an altemating-current supply line, through conductors 51 and 63, the'movable contactor 65 of a relay 67, associated with the signalling system 1, conductor 81, the signals 7, connected in parallel relationship and conductor 71, to ,the remaining bus 73 of the alternatingcurrent supply source. The stop signal 3 along the remaining highway 13 is energized from a circuit extending from one bus line 59 of the alternating-current supply source, through conductors'fil and 75, the movable contactor 77 of a second relay 79, conductor 69, the signalling lamps 3, connected in parallel relationship, and conductor 71, to'the remaining terminal 73 of the alternating-current supply source.

When a vehicle now appears along one lane (say lane 13) the exciting coil 51 of the relay 55 associated with the photc-sensitive device 25 situated in the lane is deenergized, and a circuit is closed from one bus 33 of a direction current line, through conductor 85, the movable contactor 37 of the relay 55, that has been deenergized, conductor 89, the exciting coil 91 of a time delay relay 93, and conductor 95, to the remaining direct-current bus line 97.

The time-delay relay 33 is of such structure that it closes instantly upon the excitation oi its coil 91 hutopens slowly when its coil is de energized. The relay93, therefore, remains in a closed condition for a after the vehicle has left the intersection, and the relay 55 associated with the photo sensitive device 25 has been deenergized.

The plurality ofcontactors 99, 101 and 193. When it is energized, a circuit is closed from one directcurrent hus line 83, through conductors 105 and. 197, its upper movable contactor 99, conductor 109, the lower contactor 111 of one relay 113 of a pair of relays 113 and 115 comprising an interlocking system 117, conductor 119, the exciting cell 121 of the remaining relay 115 of the interlocked pair 117 and conductor 123, to the remaining direct-current bus line 97. At the same time, a second circuit is closed, from one direct-current bus line 33, through conductors 195 and 125, the contactor 191 of the time-delay relay 93, conductor 127, a contactor 129 of.

one relay 131 of a second pair 132 of interlocked relays 131 and 133, conductor 135, the coil 137 of the remaining relay 133 of the second interlocked pair and conductor 139, to the remaining direct-current bus line 97.

It will he noted that the lane 15 at right angles to the lane 13 (heretofore considered) is equipped with a similar system of relays including the relay 57 adapted to he cleenergized from ihe photo-sensitive device 27 or 29 situated along the lane 15, and a time-delay relay 141 adapted to be energized through the contactor 143 of the relay 57 associated with the photo-sensitive devices. The time-delay relay 141 is similar to the timeprecletermined period time delay relay 93 is equipped with a delay relay 93' which was discussed hereinabove. and is equipped with a plurality of corresponding contactors 145, 147and 149 that are adapted to close corresponding circuits through the two pairs 01 interlocked relays 117 and 132. In this case, a circuit is closed through the contaotors 151 and 153 of relays 115 and 133 of pairs 117 and 132 o! interlocked relays, the exciting coils 121 and 137 oi! which'were energized in the above considered case, and through the coils 155 and 157 01' the relays 113 and 131 of the pairs, and through the lower contactors 111 and 129, 01 which the energizing currents in the above'hypothetical case passed.

It is to be noted that the activi'y of the individual relays 113, 115 and 131 and 133 in the pairs 117 and 132 are predetermined by the succession in which the street devices (say 25 and 29) are afiected by vehicles. Thus, if the vehicle first appears along one lane 13,'ihe relays 115 and 133 of the pairs are energized, and the remaining relays 113 and 131 of the pairs are prevented from becoming energized, while, if the vehicle appears first at the intersecting lane 15, the converse of the condition is produced. [is will he seen hereinafter, the interlocked relays 117 and 132 are utilized, respectively, in determining the condition of the lights and in predetermining the direction of rotation of the motor.

The lime-delay relays 93 and 141 are equipped with contactors 103 and 1&7 through which two parallel circuits are closed. One circuit extends from a direct-current bus line 33. through con ductors 105 and 159, the ccntactor 193 01 one relay 93, conductor 161, the exciting coil 153 of a third time-delay relay 155,.and conductor 167, to the remaining direct-current bus line 97, and the remaining circuit extends from one directcurrent bus line 83, through conductors 195 and 159, the con'actor 1 19 oi the remaining relay 111, conductors 159 and 131, the exciting coil 163 off the third time-delay relay 165 and conductor 157, to the remaining bus line 97 of the directcurrent source.

no The time-delay relay 1 55 is of a type, adapted to close instantly when its coil 163 is deenergized and requiring a predetermined time for opening when its coil becomes energized. it will he noted that the relay 165 can only be cleenergizecl when 5 139 Returning now to the case that was originally considered, (that is, to the case wherein a single vehicle appears along one lane 13, causing one time-delay relay 93 to become energized) it isseen that the excitation of the relay 115 of one pair 117 of interlocking relays causes a circuit to be closed from one direct-current bus line 33, through conductors 171 and 173, a movable contactor 175 of a latch relay 177, the exciting coil 179 oi which is adapted to he energized through the contactors 181 of the time-delay relay 16 5, conductors 183 and 185, a movable contactor 187 of the energized relay 115 of one pair 117 of interlocked relays, conductor 139, the exciting coil 191 of a relay 193, associated with the street signals 1 and conductor 195, to the remaining direct-current bus line 97. A second circuit is opened from one direct-current bus line 83, through conductors 171 and 173, the movable contactor 175 of the relay 177, conductor 183, a seccontactor '181 of the time-delay relay 165, con-- system 1 has been so actuated that a the particular highway 13 for which it is moving,

' lay 165, conductor 0nd movable contactor 197 of the relay 115 of the inlerlocked pair 117, that was disengaged from its corresponding fixed contacts 199 when the relay 115 was energized, conductor 201, the exciting coil 203, of the relay 79 associated with the signal lamps 1 and conductor 195, to the remaining bus line 97 of the direct-current source. When the latter relay 79 is deenergized, the circuit, through the lamps 3 that indicate stop along the highway 13, along which the vehicle appears, is broken. On the o.her hand, by reason of the fact thatthe relay 193 was simultaneously energized, a circuit is closed from one alternatingcurrent bus line 59, through conductor 61, a movable contactor 205 of the relay 193, conducor 207, the go signalling lamps 5, connected in parallel relationship and conductor 71, to the remaining terminal 73 of the alternating-current bus line. Y

It will be noted that, by the interruption of the beam exciting the photo-sensitive device 25 disposed along the highway 13, the signalling g v 5 is indicated for which the beam was energized, while the stop signal 7 for the remaining. highway 15 remains unaffected It is well to point out that an analogous system of relays is provided for opening the circuit through the stop" lights 7 that are displayed along the highway 15.and for closing the circuit for the go" lights 9- along that highway when a vehicle appears along the highway 15 instead of along the former highway 13. The circuits .as-

.sociated with these relays are similar to the circuits associated with the relays hereinabove and, therefore, will not be traced in detail.

Heretofore, the only condition considered has been that wherein a single-vehicle moving along one of the intersecting lanes 13 actuated the control system associated with that lane and, consequently, produces a condition wherein the "go" signal is displayed for the highway along and the stop" signal is displayed for the remaining highway. If a second vehicle should appear along the remaining highway 15 during the interval in which the go signal is being displayed along the first highway, the relay 57, associated with the photo-sensitive device 27 or 29 disposed on the highway, is deenergized, and a condition is obtained wherein both time-delay relays 93 and 141 are energized. The circuit through the coil 16?: of the third time-delay relay 165 is then opened, andthe 'movable contactor 181, associated with the relay, immediately engages a plurality of corresponding fixed contacts 209.

When this condition is attained, the interlocked pairsot relays 117 and 132 remain unchanged in their activity, while the coils 179 and 211 of two latch relays 177 and 213 are energized through the contactor 181 of the time-delay relay 165.

The circuit through the: coil 211 of one relay 213 extends from one direct-current bus line 83, through conductors 215 and 217, the movable ductor 219, the exciting coil 211 of one relay 213 and conductor 221, to the remaining bus line 97 of the direct current source. The circuit of the remaining relay extends from a direct-current bus line 83, through conductors 215 and 217, the movable contactor 181 of the time-delay re- 219, the exciting coil 179 pt relative electrical orientation of the discussed the relay 177 and conductor 223, to-the remaining bus line 97 o! the direct-current source.

The two latch relays 177 and 213, are, therefore, energized and are latched in their energized positions by latches 227 and 229 adapted. to be tripped by electromagnetic trippingdevices 231 and 233, the exciting circuits of which will be discussed hereinafter.

By reason oi the excitation of the relay 177, a circuit is closed Irom one alternating-current bus line 59, through conductor 235, a movable contactor 237 of the latch relay 177, conductor 239, the main windings 241 of the motor 243 that drives the program controller 245 and conductor 247, to the remaining bus line 73 of the alternating-current source.

The motor 243 that drives the program controller 245 is of the induction type and its direction of rotation is predetermined by the orientation of the terminals 249 and 251 of its main winding 241 relative to the terminals 253 and 255 of itsstarting or .teaser" winding 257. The ltteaserfii winding 257 andthe main winding 241 is predetermined by the particular relay of the interlocked pair 132 that is in an energized condition.

As has been assumed hereinabove, the relay 133 is energized and, because it is energized, the remaining relay 131 of the pair 132 is denergized in spite of the fact that both time-delay relays 105 93 and 141, associated with the p'air 132, are now energized. Consequently, a circuit is closed through the teaser winding 257 that extends from one terminal 59 of the alternating-current source, through conductor 235, the'contactor 237 of the latch relay 177, conductors 239, 259 and 260, a movable contactor 261 of the excited relay 133 of the interlocked pair 132, conductors 263 and 265, a movable contactor 267 of a reversing relay 269, the function of which will be discussed 1115 hereinafter, conductor 271, the teaser winding 257, conductors 273 and 274, the remaining movable contactor 275 of the reversing relay 269, conductors 277- and 279, a second contactor 281 of the excited relay 133 or the interlocked pair 132 and conductors 283 and 285, to the remaining bus line 73 of the alternating-current source. It is to be noted that the condition of the interlocked pair of relays has now predetermined the direction of rotation of the motor 243 if the conditionoi the reversing relay 269 is disregarded, and we shall, for the present, disregard it. If the remaining relay 131 of the pair 132 had been energized, the direction of rotation of the motor 243 would have been of opposite polarity to its present direction. The corresponding teaser coil circuit for the relay 131 extends from a bus line 59 of the alternating-current source, through conductor 235, the contactor 237 of the relay 177, conductors 239, 259 and 260, a contactor 287 of 135 the energized relay 131 of the pair 132, conductors 279 and 277, the movable contactor 275 of the reversing relay 269, conductors 274 and 273, the "teaser coil 257 of the motor.243, conductor 271, the remaining movable contactor 267 o! the reversing relay 269, conductor 265, a secondcontactor 289 of the energized relay 131 of the pair 132 and conductors 283 and 285, to the remaining bus line 73' of the altemating-current source.

'It will be noted that, while the terminals 249 and 251 of the main winding 241 were connected, respectively, to the terminals 255 and 253 of the teaser winding 257 in the. first hypothetical case, the terminals 249 and 251 of the main windmg 241 are connected, respectively, to the ter- 1,942,266 male 253 and 255 01' the teaser winding, in the latter hypothetical case. Hence, ii. the conditions of the reversing relay 269 remain unchanged, the motor 243, in the one case, rotates in a direction opposite to its direction of rotation in the second case,

It will be noted that the latch relay 177, energized from the contactor 181 of the time-delay relay 165, is equipped with a plurality of contactors 175 and 291 through which the circuits through the coils 191, 203, 293, and 295 o! the relays 193, 79, 67 and 297, associated with the signal lamps 1, are opened when the relay 177 becomes energized.

The exciting coil 01' the relay associated with the fgo lights 5 along one highway 13, was included in a circuit extending from one directcurrent bus line 83, through conductors 171 and 173, the contactor 175 o! the latch relay 177', conductors 183 and 185, the movable contactor 137 of the excited relay 115 of the interlocked pair 117, conductor'139, the exciting coil 191 of the relay 193 and conductor 195,-to the remaining bus line 97 of the direct-current supply source. The circuit is now broken by the excitation of the relay 177 and the disengagement of the contactor 175 from its corresponding fixed contacts 229.

The circuit through the exciting coil 203 of the relay 79, associated with the stop lights?! on the same highway 13, was originally opened by the excitation of the relay 115 of the interlocked pair 117 and now remains in open position, even if the circuit through the coil 121 of the relay 115 is opened, since thernovable contactor 175 of the latch relay 177 is in the circuit and is latched in open position. 1 i

The exciting coil 293 of the relay 67, associated with the stop signals 7 on the remaining highway 15, was in a circuit extending from one direct-current bus line 33, through the lead 171,

l the contacts 291 of the latched relay 177, condoctors 351 and 303, a movable contactor 305 of the unexcited relay 113 of an interlocked pair 117, conductor 397, the exciting coil 293 of the relay 57 and conductor 195, to the remaining bus line 97 of the direct-current supply source. The circuit is now broken by the disengagement of the contactor 291 from its fixed contacts 339.

The exciting coil 295 of the relay 297. associ-v ated with the go signal 9 of the highway 15,

is in open position by reason of the fact that its circuit is broken iwtween the fixed contactors 311 of the unexcited relay 1130f the pair of interlocired relays 117. The circuit also contains the fixed contacts 309 of the latch relay 177 which are not engaged by the corresponding movable contactor 291 by reason of the fact that therelay 177 is energized and latched in the energized condition.

On the other hand, it should be noted that the relays 193, 79, 67 and 297 are successively energized through the brushes 313 or 315 and 317 of the program controller 245. However, before this condition is attained, the brushes 313 or 315 must engage the conducting segment 319 of the controller 245 and, consequently, the caution signals 11 are displayed. The circuit of the caution signals 11 extends from one alternatingwurrent bus line 59, through conducting 321, the movable contactor 323- 01 the relay 297,

associated with the go signals 9 along one highway 15, conductor 325, the movable contactor 327 of the relay 67, associated with the stop" signals 7 along the same highway, conductor 329, the movable contactor 331 of the relay 193, as-

sociated with the signals 5 along the remalning highway 13, conductor 333, the movable,

contactor 335 of the relay 79, associated with the stop signal 3 along the remaining highway 13, conductor 337, the "caution" signals 11 connected in parallel relationship and conductor 71, to the remaining bus line 73 oi. the alternating-eurrent source.

The motor 243 is now rotating in a direction predetermined by the condition of the relay system and this direction is of such polarity that the lane 13 along which the original go signal 5 was displayed retains this signal after the cau tion signal 11 is displayed. With reference to the drawings, the program controller 245 is now ro-' toting in a counter-clockwise direction. Consequently, the circuits through the exciting coils 191 and 293 of the relays 193 and 67, associated with the go signals 5 along one highway 13, and the stop signals 7, along the remaining highway 15, are energized.

The circuits through the coil 191 of the relay 193, associated with the go" signal 5, is as follows: from one direct-current bus line 83 through conductors 171 and 339, a movable cont actor 341 of the second latch relay 213, .excited from the time-delay relay 165, conductor 343, the brush 317 adapted to engage aflcolla'r 345 on the shaft 347 of the program-control motor 243, the conducting segment 319 of the program controller 245, the brush 313, now in engagement with the conducting segment 319, conductors 349. 307 and 351, a second contactor-353 of the latch relay 213. conductors 355 and 189, the exciting coil 191' of the relay 193. associated with the go" signal 5, andconductor 135, to the remaining bus line 97 of the direct-current source.

The exciting coil 293 of the relay 67, associated with the stop signal on the highway 15, is also energized through the program controller 245, the circuit being as follows: from one directcurrent bus line 83, through conductors 171 and 339, the movable contactor 341 of the relay 213. conductor 343, the brush 317 of the program controller 245, the collar 345 on the shaft 347 of the program-control motor 243, the conioo 245, the brush 313 in engagement therewith, conductors 349 and 307, the exciting coil 293 of the relay 57 andconductor 195, to the remaining bus line 97 of the direct-current source.

As long as the brush 313 continues in engagement with the conducting segment 319 of the program controller 245, the two relays 193 and 67, associated with the signalsl at the inter-- section-12, are energized. The circuits through the contactors of these relays have been traced hereinabove and it is noted'that a go signal 5 is indicated for the highway 13, while the stop signal is displayed along the remaining highway 15.

When the program controller 245 rotates to such point that the first brush 313 is disengaged from the conducting segment 319, the relays 193 and 67 are again deener'gized, and the caution signal 11 is displayed along both highways. At the same time, a circuit is completed from one direct-current bus line 83, through conductors 215 and 357, the exciting coil 359 of one trip relay 233, conductors 361 and 363, the contactors 365, 367, 369 and 371 of the relays 193, 79, 67 and 297, associated with the signalling system 1, to the remaining bus line 97 of the direct-current source. A second and similar circuit is also com- 79, associated with I motor 243 is dependent on pleted through the coil 373 of the relay 231, associated with the latch 227 of the relay 177, the coil 373 of the latter relay 231 being in parallel with the coil 359 of the former trip relay 233.

The latches 227 and 229 are, therefore, removed, and the cores 375 and 377 of the latch relays 177 and 213 arefree to drop if the circuitsthrough their coils 179 and 211 are open. However, it is to be noted that the circuits through the coils- 179 and 211 are broken only through the contactor 181 of the time-delay relay 165. The relay 165 is of such structure that its core 379 is not raised for a period sufficient to give the segment 319 on the program controller 245 sufiicient time to move into engagement with the remaining brush 315.- The exciting coils 295 .and 203 of the relays 297 and the stop" signals 3 and the go signals 9 on the highways 13 and 15, respectively, are, therefore, energized, and the go" signal 9 is displayed along the highway 15, while the stop signal 3 is displayed along the highway 13. The circuits through the coils 295 and 203 of the relays 297 and 79 are similar to the circuits through the coils 191 and 293 of the other two relays 193 and 67 and, therefore, need hardly be traced herein.

When the program controller 245 rotates to the position wherein the brushes 313 and 315 are again not in engagement with the conducting segment 319, the trip coils 359 and 373 are again energizedand, unless the time-delay relay 165 has been reenergized by the presence of a vehicle along both highways 13 and 15, the latch relays 177' and 213, being deenergized, their cores 375 and 377 and the system revert to their original conditions.

It is to be noted that the conducting segment 319 of the program controller 245may stop in either of two positions relative to the brushes 313 and 315. That is to say, it may stop in the position indicated in the drawings or it may stop in a position 180 therefrom. The position in which the conducting segment 319 of the program controller 245 stops is determined by the condition of the intersection when the latch relays 177 and 213 are tripped.

It is seen that the direction of rotation of the the position in which the conducting segment 319 of the program controller 245 is oriented when the program controller stops. For this reason, the reversing relay 269 is provided, and its movable contactors 267 and 275 are so adjusted that the direction of rotation of the motor 243 is polarized in accordance with the latest position of the programcontrol conducting sector 319.

The circuit through the coil of the reversing relay extends from one direct-current bus line 97, through conductor 379, the coil 381 of the reversing relay 269, conductor 283, one brush 285 associated with 'a disc 287 supported on the shaft 347 of program-control motor 243, a conducting segment 389 on the disc 287, if the conducting segment 319 of the program controller 245 is 'motor 243, a brush 393 engagingthe collar 391 and conductor 395, to the remaining direct-cur rent bus line 83.

It will be noted that, for the condition illustrated in the drawings, the reversing relay 269 is deenergized. However, if the program controller stops in a position 180 from the position shown, the reversing relay 269 is energized, and the direction of rotation of the motor, as predetermined by the interlocked relays 131 and 133, is reversed by the reversing relay 269.

In the described embodiment, my invention has been'illustrated as applied to a specific system of relays. It is to be noted that my invention may be practiced with a system unlike that herein set forth. In the present embodiment of my invention, eighteen relays are incorporated. It will be recognized that many combinations may be atdash-pot relays, is to be regarded only as symbolical as time-delay relays are well known in the art and a relay of any well known type may be utilized.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that-many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claim.

I claim as my invention:

A traffic control system for a plurality of highways comprising trafiic signalling means provided with stop, caution and go signals for each ,of. said highways, means cooperating with said signalling means to normally energize said stop signal for all of said highways, means to be vehicle actuated disposed on each of said highway, means to respond to the vehicle responsive means on one of the highways when it is actuated by a vehicle moving along said highway to deenergize ,the stop signal and to energize the go signal for the said highway, means responsive to the vehicle responsive means on another highway when it is 125 actuated within a predetermined time of the actuation of said first named vehicle responsive device to deenergize said stop signal and to energize the go signal for said last named highway, at

least a predetermined period of time after said 13 

